For preparing a water repellent surface, a treatment of coating or deposition, on the surface, a highly water repellent material, for example, a higher fatty acid, fluoro-containing higher fatty acid or wax is usually conducted. This treatment can provide an contact angle with water to about 80 to 120.degree. for a smooth surface to be treated. By utilizing such a water repellent nature, water repelling technique has been applied generally to a wide variety of fields such as umbrellas, window glass of cars, roofs and parabola antennas.
For further increasing the contact angle, it is possible to provide a greater contact angle by forming appropriate roughness on the surface to be coated with the material described above. The contact angle with water of the surface can be increased to 150.degree. or more by such a method.
Generally, if the contact angle with water is 150.degree. or more, the surface is referred to as super-water-repellent. Since water assumes a form of a nearly spherical shape on the surface, if the surface is slanted slightly, such water sphere tumbles down like a glass bead. Further, when an article with a surface showing the super-water-repellency is placed in water, the super-water-repellent surface forms a mirror face depending on the angle observed. As an example of showing super-water-repellency, there can be mentioned, for example, plant leaves. Most of plant leaves keep the contact angle with water at 150.degree. or more due to roughness of a wax on the surface and we often observe that water droplets such as dewdrops tumble down from leaves.
By utilizing this phenomenon, it has been studied to make evaporator fins of air conditioners or radio antennas.